The total antioxidant capacity of human serum measured using enhanced chemiluminescence is almost completely accounted for by urate.

Abstract

Free radical reactions are strongly implicated in the pathogenesis of many diseases.' Pro-oxidative free radicals can potentially be chemically neutralized by naturally occurring antioxidants in biological fluids. A number of components present in serum have been shown to possess chain breaking antioxidant capacity including vitamins C and E, bilirubin, urate and protein thiols in aqueous or organic solution in vitro.i: Measurement of total antioxidant capacity (TAC) of biological fluids is believed to be a useful measure of the ability of antioxidants present in the fluids to protect against oxidative damage to membranes and other cellular components. The large variety of components of serum with potential antioxidant capacity has led to the development and widespread use of assays which claim to measure TAC, thereby providing a clinically useful global measure. A number of methods have been developed over the past few years which allow the rapid and simple measurement of TAC of serum.s As part of a reference value study on serum biochemistry being conducted concurrently in the laboratory we undertook an investigation to measure the total antioxidant capacity of serum samples. The 41 volunteers in the study were normal healthy non-smokers aged 19-59 [mean 32·9 (SD lOA)] who had not taken any medication or alcohol in the 5 days prior to blood collection. Whole blood 6 mL was collected between 0800 and 1000 h into SST Vacutainer tubes for biochemical investigations. Measurement of urate, total bilirubin, and total protein were carried out on a Technicon AXON analyser. The enhanced chemiluminescent